/Engine/Source/Runtime/Engine/Classes/PhysicsEngine/ConstraintInstance.h
Sets the Linear XYZ Motion Type and the limit distance (Note distance is the same for all 3 axes)
void SetLinearLimits ( ELinearConstraintMotion XConstraintType, ELinearConstraintMotion YConstraintType, ELinearConstraintMotion ZConstraintType, float InLinearLimitSize )